A GENERAL-MODEL FOR SORPTION HYSTERESIS IN FOOD MATERIALS

A hypothesis is proposed in this study to account for the origin of so rption hysteresis. The hypothesis is based on the published research e vidence that during a sorption process phase change within a material causes temperature gradients which induces heat transfer. The rate of heat transfer in turn greatly influences phase changes and mass transf er leading to the redistribution of the sorbate during a sorption proc ess. Hysteresis is a result of the sorbate mass redistribution. It is shown thermodynamically that sorbate mass redistribution or rather hys teresis, is an inherent process in order for a material to protect its elf from distortion under the extremity of local temperature alteratio n. Based on the proposed hypothesis, a general mathematical model is d eveloped to quantify the hysteresis loop. The model agrees with the pu blished hysteresis data for food materials. (C) 1997 Elsevier Science Limited. All rights reserved.